root/src/pkg/crypto/rc4/rc4_arm.s

// Copyright 2013 The Go Authors. All rights reserved.
// Use of this source code is governed by a BSD-style
// license that can be found in the LICENSE file.

#include "../../../cmd/ld/textflag.h"

// Registers
dst = 0
src = 1
n = 2
state = 3
pi = 4
pj = 5
i = 6
j = 7
k = 8
t = 11
t2 = 12

// func xorKeyStream(dst, src *byte, n int, state *[256]byte, i, j *uint8)
TEXT ·xorKeyStream(SB),NOSPLIT,$0
        MOVW 0(FP), R(dst)
        MOVW 4(FP), R(src)
        MOVW 8(FP), R(n)
        MOVW 12(FP), R(state)
        MOVW 16(FP), R(pi)
        MOVW 20(FP), R(pj)
        MOVBU (R(pi)), R(i)
        MOVBU (R(pj)), R(j)
        MOVW $0, R(k)

loop:
        // i += 1; j += state[i]
        ADD $1, R(i)
        AND $0xff, R(i)
        MOVBU R(i)<<2(R(state)), R(t)
        ADD R(t), R(j)
        AND $0xff, R(j)

        // swap state[i] <-> state[j]
        MOVBU R(j)<<2(R(state)), R(t2)
        MOVB R(t2), R(i)<<2(R(state))
        MOVB R(t), R(j)<<2(R(state))

        // dst[k] = src[k] ^ state[state[i] + state[j]]
        ADD R(t2), R(t)
        AND $0xff, R(t)
        MOVBU R(t)<<2(R(state)), R(t)
        MOVBU R(k)<<0(R(src)), R(t2)
        EOR R(t), R(t2)
        MOVB R(t2), R(k)<<0(R(dst))

        ADD $1, R(k)
        CMP R(k), R(n)
        BNE loop

done:
        MOVB R(i), (R(pi))
        MOVB R(j), (R(pj))
        RET